Gas pressure formed obturator



Oct. 16, 1962 A. J. GRANDY GAS PRESSURE FORMED OBTURATOR Filed Jan. 18, 1960 INVENTOR. ANDREW J. GRANDY United States Patent Office 3,058,424 Patented Oct. 16, 1962 3,058,424 GAS PRESSURE FORMED OBTURATOR Andrew J. Grandy, 2707 Grant Ave., North Hills, Pa. Filed Jan. 18, 1960, Ser. No. 3,210 1 Claim. (Cl. 10294) (Granted under Title 35, US. Code (1952), see. 266) The invention described herein may be manufactured and used by or for the Government for governmental purposes without the payment to me of any royalty thereon.

This invention relates to means for obturating a gun barrel, and more especially to means adapted to form an obturator in response to the gas pressure incident to the firing of a projectile.

This obturator is applicable to both smooth bore and rifled barrels. As applied to smooth barrels, it is tailor made to the particular barrel with which it is used. As applied to rifled barrels, it functions both as an obturator and a rotating band. It thus has the advantage that it is usable with difierent types of guns, simplifies the manufacture of ammunition by eliminating the necessity for the conventional rotating band, and provides a rotating band in the case of rifled barrels without imposing axial forces on the gun barrel.

The invention will be better understood from the following description when considered in connection with accompanying drawings and its scope is indicated by the appended claims.

Referring to the drawings:

FIG. 1 illustrates a form of the invention wherein the deformable member is a washer and has pressure applied to it through a metal disk,

FIGS. 2 and 3 show embodiments wherein the obturator forming pressure is applied directly to a deformable FIG. 4 illustrates an arrangement wherein the pressure is applied to the deformable member through a metal ring, and

FIG. 5 illustrates a modification wherein a deformable ring is located in a channel which abuts the rear end of the projectile.

In the arrangement of FIG. 1, the body of a projectile has a nose portion 8 and a tail portion 9. The tail portion has at its rear end a recess which encloses a deformable washer 11 and has a thin outer wall or overhanging lip 12. Slidable within this recess is a metal disk 13 which is maintained in alinement with the axis of the projectile by cap screws 14.

When this projectile is fired from a gun barrel 7, the generated gas pressure forces the disk 13 against the washer 11 which is so compressed that it forces the wall 12 outwardly thus forming an obturator to the exact dimension of the bore of the barrel.

In the embodiment of FIG. 2 an annular groove 15 at the base of the projectile 10 encloses a deformable ring 16 which is acted upon directly by the gas pressure to force the outer wall of the groove radially outward into contact with the inner periphery of the barrel.

In FIG. 3, the groove has two levels 17 and 18 and the thin wall section 12 is relatively long. This groove is of such depth that a portion of the wall 12 can be crimped to hold the deformable ring 16 in the groove. In the operation of this modification, the ring is forced into the smaller part of the groove making for more effective use of the ring and pressure.

The modification of FIG. 4 differs from that of FIG. 3 in that the groove or recess is of rectangular shape and the gas pressure is applied through a metal ring or ham mer 20 which is slidable within the groove. Application of pressure to the hammer will compress the deformable ring 16 which in turn will force the outer wall of the groove radially outward into contact with the inner periphery of the barrel.

FIG. 5 shows an arrangement including a channel shaped ring 21 which is tightly fitted to the base of the projectile and encloses the deformable ring. Slidable within this channel is a metal ring 22 through which pressure is applied to the ring which in turn compresses the deformable ring 23 for forcing the wall of the channel out against the inner periphery of the barrel.

As will be appreciated by those skilled in the art, the present invention provides a more elfective means of obturating a gun barrel, simplifies the manufacture of ammunition by dispensing with conventional rotating bands, avoids the imposition of rotating band engraving forces on the gun barrel, and permits the use of projectiles of various lengths in one weapon without having to resort to the COIlILEIbOlES used heretofore.

A feature of this invention is the provision of a lip 21 (FIG. 5) having one end unsupported and capable of being flexed radially outward by deformable material 23 a greater amount than would be the case were said ring 22 and material 23 absent. Assuming lip 21 in FIG. 5 to be drawn to scale the axial length of said lip is at least about 4 times its radial depth or thickness. A supporting floor 25 is radially spaced from said lip a distance less than the lip length. Abutment wall 24 is connected to both floor 25 and lip 21 with the result wall 24 will not rise under thrust of material against the lip 21 because an equal opposite thrust of material 23 is downward against floor 25 and wall 24 is connected to both lip 21 and floor 25. Those familiar with interior ballistics will understand that the materials numbered 22 and 23 have a smaller mass than the projectile body and will therefore be moved sooner, through perhaps by only a millisecond or much less time before the projectile starts moving forward but by enough time to enable the lip 21 to be flexed radially outward to be useful in elfecting obturation. The metal ring 22 being substantially tangent to the deformable ring 23 may be viewed as assisting in radial outward expansion or deformation of ring 23, against the lip 21 at location 26.

I claim:

A projectile body having front and rear end portions and having a cylindrical rear portion of reduced diameter coaxial with said body and forming an annular shoulder at a connecting junction therebetween, the combination therewith providing an obturator radially outside said portion of reduced diameter and longitudinally adjacent its body junction, said obturator including an annular flexible lip secured to said body, said lip being of substantially uniform radial thickness, having a rear end unsupported and free to be flexed radially outward about its supported front end, the outside diameter of said lip When unflexed being substantially that of said projectile body, said projectile being provided with an annular space radially inward of said lip and generally coaxial with said projectile, said space being bounded on the radial outside by an under surface of said lip, on the front by an abutment wall surface, on the radial inside by a surface on said portion of reduced diameter as a floor, and on the rear side by a metal hammer ring, the radial depth of said space beneath said lip being less than the longitudinal length of said lip, said abutment wall surface being connected to said floor surface and to said lip, and a deformable ring of material within said space, of generally circular cross section before being deformed, contiguous to the under surface of said lip, to said abutment wall surface, to said floor surface, and to a front face of said metal hammer ring, said hammer ring being of generally rectangular shape, contiguous to said deformable material, to said lip, and to said floor surface, whereby upon impact of propellant pressure to a rear of said deformable material and flexure of said lip radially outward into tight contact of the free end of said lip with an inner surface of a gun barrel and whereby said lip rear end may be moved outward a greater distance than said deformable material needs to be radially elongated.

References Cited in the file of this patent UNITED STATES PATENTS Hotchkiss May 14, 1861 Alexander Jan. 7, 1862 Allan July 9, 1957 

